Thermal and mechanical evaluations of asphalt emulsions and mixtures for microsurfacing

In this study, four different emulsifiers were used to prepare asphalt emulsions. The effects of emulsifiers on emulsion stability were investigated using the storage stability test, laser particle size analyzer (LPSA), and differential scanning calorimetry (DSC). Furthermore, aggregate (0.15–0.3 mm) was mixed with asphalt emulsions to obtain emulsified asphalt mortar. The Brookfield rotational viscometer (BRV) was employed to determine the mortar viscosity and equilibration time. According to the laboratory results, the storage stability of asphalt emulsions were in agreement with the corresponding particle size and specific surface area. There was a linear relationship between the square of particle size and storage stability. In addition, the QA-emulsifier-prepared asphalt emulsion yielded the smallest particle size and greatest specific surface area. This indicated the QA asphalt emulsion had the highest storage stability, which was followed by AA, XA, and IM asphalt emulsion, respectively. The DSC results showed that the enthalpy change displayed a linear relationship with the equilibration time. It was also demonstrated that the XA asphalt emulsion had the highest thermal stability, which was followed by AA, IM, and QA asphalt emulsion, respectively. This implied that there was no consistent ranking between storage stability and thermal stability. Finally, the AA asphalt emulsion was selected to prepare microsurfacing mixtures. The performance tests results indicated that aggregate gradation, aggregate temperature, additional water content, cement content and sand equivalent affected the mixing time and demulsification time dramatically. The wet-track abrasion test (WTAT) results demonstrated that mixtures with higher asphalt emulsion content and sand equivalent tended to have a higher early strength and a lower moisture susceptibility.